The crane operator who was due to be in his cabin when the helicopter crashed into it escaped because he was running late for work, it was claimed.

Site workers said the man had never been late before, but was understood to have been held up while dropping his children off at school.

"He would have been wiped out if he had been on time," said Paul Robinson, 42, a lorry driver and a father-of-two, from Dagenham, Essex. "It was a very lucky escape."

He said he was "100% sure the man would have been killed if he had already been in position".

A spokesman for Berkeley Group, the developer of St George Wharf Tower, contradicted reports that said the crane operator, who has not been named, was climbing the shaft when the crash happened. A spokesman said no one was in the crane or ascending its tower when the helicopter struck.

Robinson, who collects waste from the site, was in a queue waiting to drive in when he felt a bump, jumped out of his lorry and saw a ball of fire. "I just ran. I panicked. My mind went blank and fuzzy," he said.